Closed workpieces, e.g. punching or cutting tools have in many cases the feature that the contour to be cut with the electrode is not reachable from the outside, because the workpiece walls block access of the electrode and the guide means carrying the electrode. FIG. 1a shows such a cutting tool. The spatial dimensions are length 3 m, width 2 m and height 1.5 m. Such a cutting tool is used for cutting sheet metal parts such as e.g. automobile bodies after thay have been shaped. As is shown, after shaping, said sheet metal parts have material projecting beyond the shape limits. This material must be cut off by the cutting tool shown in FIG. 1a. The manufacture of such a cutting tool is very complicated, because the contour to be cut out represents a closed inner shape. An erosion machine can only cut this contour if the wire guide is particularly long. However, this means a considerable vibration of the electrode during the erosion process. Thus, the requisite precision would not be maintained. The cutting tool can obviously have smaller spatial dimensions than those of FIG. 1a. In the case of a smaller tool, an erosive cutting machine could not cut the closed inner shape, even with lengthened wheel guidance means. FIG. 1b shows a punch having a closed outer shape and can either be a blanking punch or a cutting punch. The external dimensions of the punch can be up to a few meters. The closed outer shape of the punch cannot be machined in one operation with the known working methods, because it is fixed in a clamping system and the working machine, e.g. the erosive cutting machine, would collide with the clamping system. To avoid such a collision, the closed outer shape can only be machined in parts. The punch must then be reclamped in the clamping system and the new alignment then takes place between punch and erosive electrode. As a result of these difficulties, manufacture of such cutting and punching tools has taken a considerable time and is very complicated, which leads to high costs.